1. Field of the Invention
The present invention generally relates to a syringe, and more particularly, to an auto-disable safety syringe having a barrel and a needle seat, in which the needle seat of the syringe can be not only engaged securely with the barrel but also released easily from the barrel of the syringe so as to allow a needle being fully retracted inside the barrel by a plunger, so that the needle is prevented from pricking, scratching or other harmful exposure to medical staffs during subsequent handling of the self-destructed syringe, thus achieving a dual protection of patients and medical staffs.
2. Background of the Related Art
Medically, a disposable syringe is widely used in order to avoid cross contaminations. Conventionally, a medical staff breaks a plunger of the disposable syringe after an injection so as to achieve the disposable purpose. However, the auto-disable syringe still tends to prick or scratch the medical staff during its subsequent handling, this may cause a further contamination, so that the conventional disposable syringe could not achieve a “dual protection”, that is, the conventional syringe could not protect both medical staffs and patients simultaneously.
Recently, for protecting both medical staffs and patients, there have been proposed safety syringes, some of which have been filed for patents, such syringes employ a structure with a manually retractable needle. With the structure, a plunger and a needle seat are connected and interlocked with each other after an injection of syringe, then both the needle seat and the needle are retracted inside the barrel by the plunger when the plunger is manually drawn back. This structure could prevent the used needle from pricking the medical staff. However, the above safety syringe with a manually retractable needle has a problem in connection between the needle seat and the barrel. Conventionally, the needle seat is connected to the barrel by a rubber ring, or an interference fit between a convex ring, a boss or a convex hoop formed integrally on a needle assembly or the needle seat and a certain portion of the barrel. The above connection should be firm and could not be too firm, if the connection is too firm, the needle seat may not be pulled inside the barrel after injection and during destruction, if the connection is not sufficient firm, the injectant may be leaked out and the needle may be automatically retracted during injection, the automatic retraction of the needle will cause that the injection could not be performed. In the prior art, there is provided a syringe in which the needle seat is provided with thread, the needle seat is securely connected to a barrel of the syringe through threaded engagement therebetween, however, in order to release the needle seat from the barrel, the threaded engagement must be manually released directly or indirectly, so that the releasing operation depends on the subjective consciousness of an operator, then there may be a hidden trouble that the syringe is not destructed after use, that is, the syringe is not disposable. Meanwhile, the needle provided with thread is not a standard needle, thus causing the medical staff inconvenient to change needles during use.
In a word, it is in urgent need of providing a safety syringe which can protect both medical staffs and patients simultaneously.